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Abstract

By out-of-particle surface plasmon (SP) excitation in the near infrared range, the influences of key parameters on the basic optical properties of the Au crescent are qualitatively studied from the mode dispersion. Based on the coherent control of SP wave, a crescent pair sensor with the intensified extracted signal and the controllability of sensing is proposed. In addition, the crescent half replaced by Ag functioning as a position detector is also proposed. The particular phase of the detecting light as a detection parameter is used to improve the accuracy of the position detection.

Figures (6)

(a) Schematic diagram of the nanocrescent. (b), (d), (f) Field distributions of the component Ex, Ez and Hy, respectively. (c), (e) Magnified field distributions of Ex and Ez near the nanotips, respectively. (g) Enhancement of the Poynting vector.

Resonant spectra as the refractive index nsensor of the airhole (a) or the background (b) is increased from 1.0 to 1.5. The right upper insets in (a) and (b) are the shifts of the resonant peak caused by the increased nsensor in two different ways, which are shown in the corresponding left lower schematic diagrams, respectively.

Resonant spectra of the coherent control. The right upper inset is the extinction ratio, and the right lower inset is the structure of the crescent for interference, in which two red dots represent two light sources.

Resonant peak shifts as nsensor of the sensing and controlling unit of the crescent pair sensor is increased from 1.312 to 1.352 (the glucose solution with different concentrations) in the increment of 0.01. The sensitivity of the sensor is 412 nm/RIU by the line of best fit with the slope k = 0.412. The right lower inset is the component field distributions of the sensor as nsensor = 1.312.

Schematic diagrams of the crescent as a position detector for (a) the single signal source detection and (b) the coherent detection based on the interference of the signal source and the detecting source.